不同降水年型水氮运筹对冬小麦耗水和产量的影响

灌水和施氮是影响农田生态系统粮食生产的2个主要因素,但其增产效应和资源利用效率会受降水年型的影响。该研究基于2011—2014在陕西关中平原进行的3 a冬小麦水氮耦合试验,分析了不同降水年型下水氮管理对土壤含水率、籽粒产量、耗水量(water consumption,ETa)及产量与耗水量关系的影响。结果表明:7—9月总降水量每增加1 mm,小麦播前0~180 cm土壤底墒增加0.47 mm。随着灌水量增加,产量和ETa均增加,但仅在降水较少的2012—2013年增产显著,对水分利用效率(water use efficiency,WUE)的影响不显著;随着施氮量增加,ETa变化不显著,但其增产效果显著,使WUE显著提高,表明施氮增加了作物蒸腾占农田耗水量的比例。根据3 a各处理冬小麦产量和ETa数据,进一步探讨了在一定水分消耗下能达到的最大(边界)产量和WUE,建立了关中平原冬小麦的产量-耗水量边界方程;当ETa超过388 mm时,产量稳定在8 184 kg/hm2,WUE的最大值为2.52 kg/m3。研究可为制订合理的冬小麦水肥管理措施提供科学依据。

Effects of irrigation and nitrogen application on water consumption and yield of winter wheat in different precipitation years

Abstract: Irrigation and nitrogen fertilization are two major factors influencing the grain yield production in agroecosystem, and appropriate irrigation and nitrogen fertilizer application can improve grain yield and water use efficiency by alleviating the stress of drought and nutrient deficiency, enhancing photosynthetic area and photosynthetic rate. In this study, we investigated the impact of precipitation year patterns on crop yield, water consumption and their relationship under different water and nitrogen management practices. A field experiment during 2011-2014 was conducted with 3 irrigation levels and 4 nitrogen input levels in Guanzhong Plain of Shaanxi Province. Irrigation levels included no irrigation, irrigation 46 mm at the jointing stage, and irrigation 46 mm at the jointing and wintering stages, respectively. The nitrogen input levels included nitrogen application rate of 0, 105, 210 and 315 kg/hm2. The fertilizer was urea. The other field management followed local traditional methods. The experiment was carried out by completely randomized design. Soil water content and grain yield were measured and the water use efficiency was calculated as the ratio of yield to ETa under various water and nitrogen management in different year patterns. Meanwhile, soil water storage was calculated based on the volumetric water content. Water consumption (ETa) was calculated by the field water balance equation. The results showed that soil water content before sowing was affected by irrigation, nitrogen fertilizer application rate and precipitation. The soil water storage before sowing increased as more irrigation and less nitrogen application rate were applied. The 0-100 cm soil water storage before sowing would be supplemented majorly when the total precipitation from July to September was below 400 mm, and the 0-180 cm soil water storage before sowing increased by 0.47 mm as the total precipitation from July to September increased 1 mm. The 0-180 cm soil water storage at harvest improved with more irrigation but decreased first and then leveled at a certain value as more nitrogen was used, and it was greatly influenced by the precipitation of 2 months before harvest. Water consumption increased with more irrigation while the effect of nitrogen and interactive effect of irrigation and nitrogen on water consumption was not significant, and it has a linear relationship with water input during the growing period with the coefficients being influenced by initial soil water conditions, i.e. less water would be consumed led by unit water input when the soil water storage before planting was higher. Irrigation enhanced both the yield and actual water consumption, while the yield was only improved significantly in relatively dry year 2012-2013 and the water use efficiency were not boosted in all years; Nitrogen fertilization had no significant effect on water consumption but improved yield and water use efficiency significantly, which showed that nitrogen application rate increased the proportion of crop transpiration to total water consumption. Additionally, the maximum (boundary) yield and water use efficiency were explored by developing a boundary function of winter wheat yield and evapotranspiration in Guanzhong Plain. From the function, we found that when the water consumption exceeded 388 mm, the grain yield would level at 8 184 kg/hm2 and the maximum water use efficiency was 2.52 kg/m3. In this research, the interactive effects of water, nitrogen and precipitation year patterns on yield and field water consumption were analyzed, aiming at providing valuable information for developing reasonable water and fertilizer management practices in winter wheat production.